/* Copyright (C) 2000 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*
  get_ptr_compare(len) returns a pointer to a optimal byte-compare function
  for a array of stringpointer where all strings have size len.
  The bytes are compare as unsigned chars.
  */

#include "mysys_priv.h"
#include <myisampack.h>

static int ptr_compare(uint *compare_length, uchar **a, uchar **b);
static int ptr_compare_0(uint *compare_length, uchar **a, uchar **b);
static int ptr_compare_1(uint *compare_length, uchar **a, uchar **b);
static int ptr_compare_2(uint *compare_length, uchar **a, uchar **b);
static int ptr_compare_3(uint *compare_length, uchar **a, uchar **b);

/* Get a pointer to a optimal byte-compare function for a given size */

qsort2_cmp get_ptr_compare(uint size)
{
  if (size < 4)
    return (qsort2_cmp)ptr_compare;
  switch (size & 3)
  {
    case 0:
      return (qsort2_cmp)ptr_compare_0;
    case 1:
      return (qsort2_cmp)ptr_compare_1;
    case 2:
      return (qsort2_cmp)ptr_compare_2;
    case 3:
      return (qsort2_cmp)ptr_compare_3;
  }
  return 0; /* Impossible */
}

/*
  Compare to keys to see witch is smaller.
  Loop unrolled to make it quick !!
*/

#define cmp(N)             \
  if (first[N] != last[N]) \
  return (int)first[N] - (int)last[N]

static int ptr_compare(uint *compare_length, uchar **a, uchar **b)
{
  reg3 int length = *compare_length;
  reg1 uchar *first, *last;

  first = *a;
  last = *b;
  while (--length)
  {
    if (*first++ != *last++)
      return (int)first[-1] - (int)last[-1];
  }
  return (int)first[0] - (int)last[0];
}

static int ptr_compare_0(uint *compare_length, uchar **a, uchar **b)
{
  reg3 int length = *compare_length;
  reg1 uchar *first, *last;

  first = *a;
  last = *b;
loop:
  cmp(0);
  cmp(1);
  cmp(2);
  cmp(3);
  if ((length -= 4))
  {
    first += 4;
    last += 4;
    goto loop;
  }
  return (0);
}

static int ptr_compare_1(uint *compare_length, uchar **a, uchar **b)
{
  reg3 int length = *compare_length - 1;
  reg1 uchar *first, *last;

  first = *a + 1;
  last = *b + 1;
  cmp(-1);
loop:
  cmp(0);
  cmp(1);
  cmp(2);
  cmp(3);
  if ((length -= 4))
  {
    first += 4;
    last += 4;
    goto loop;
  }
  return (0);
}

static int ptr_compare_2(uint *compare_length, uchar **a, uchar **b)
{
  reg3 int length = *compare_length - 2;
  reg1 uchar *first, *last;

  first = *a + 2;
  last = *b + 2;
  cmp(-2);
  cmp(-1);
loop:
  cmp(0);
  cmp(1);
  cmp(2);
  cmp(3);
  if ((length -= 4))
  {
    first += 4;
    last += 4;
    goto loop;
  }
  return (0);
}

static int ptr_compare_3(uint *compare_length, uchar **a, uchar **b)
{
  reg3 int length = *compare_length - 3;
  reg1 uchar *first, *last;

  first = *a + 3;
  last = *b + 3;
  cmp(-3);
  cmp(-2);
  cmp(-1);
loop:
  cmp(0);
  cmp(1);
  cmp(2);
  cmp(3);
  if ((length -= 4))
  {
    first += 4;
    last += 4;
    goto loop;
  }
  return (0);
}

void my_store_ptr(byte *buff, uint pack_length, my_off_t pos)
{
  switch (pack_length)
  {
#if SIZEOF_OFF_T > 4
    case 8:
      mi_int8store(buff, pos);
      break;
    case 7:
      mi_int7store(buff, pos);
      break;
    case 6:
      mi_int6store(buff, pos);
      break;
    case 5:
      mi_int5store(buff, pos);
      break;
#endif
    case 4:
      mi_int4store(buff, pos);
      break;
    case 3:
      mi_int3store(buff, pos);
      break;
    case 2:
      mi_int2store(buff, pos);
      break;
    case 1:
      buff[0] = (uchar)pos;
      break;
    default:
      DBUG_ASSERT(0);
  }
  return;
}

my_off_t my_get_ptr(byte *ptr, uint pack_length)
{
  my_off_t pos;
  switch (pack_length)
  {
#if SIZEOF_OFF_T > 4
    case 8:
      pos = (my_off_t)mi_uint8korr(ptr);
      break;
    case 7:
      pos = (my_off_t)mi_uint7korr(ptr);
      break;
    case 6:
      pos = (my_off_t)mi_uint6korr(ptr);
      break;
    case 5:
      pos = (my_off_t)mi_uint5korr(ptr);
      break;
#endif
    case 4:
      pos = (my_off_t)mi_uint4korr(ptr);
      break;
    case 3:
      pos = (my_off_t)mi_uint3korr(ptr);
      break;
    case 2:
      pos = (my_off_t)mi_uint2korr(ptr);
      break;
    case 1:
      pos = (my_off_t)mi_uint2korr(ptr);
      break;
    default:
      DBUG_ASSERT(0);
  }
  return pos;
}
